Dipole Moment Of Water Molecule Research Articles

Effect of magnetization conditions on the slump and compressive strength of magnetized water concrete

Magnetized water (MW) technology uses a magnetic field to affect the dipole moment of water molecules, changing the hydrogen bonding between them. As a result, the physical and chemical properties of water are altered. MW has the potential to reduce the need for admixtures and cement while preserving the desired strength and workability of concrete. However, the exact mechanisms by which different magnetization conditions improve concrete properties remain unclear. This study explored the effects of magnetic field intensity and water flow velocity on the workability and compressive strength of concrete using a custom-built magnetization device. Twelve distinct MWs were prepared under varying magnetic field intensities (210, 230, 250, and 270 mT) and water flow velocities (0.5, 0.6, and 0.7 m/s), and the performance of the concrete was assessed by slump and compressive strength tests. Additionally, the physicochemical properties of the MW were examined. The research results indicated the presence of significant interactions between the magnetization parameters. When the water was magnetized at a flow velocity of 0.7 m/s, and combined with magnetic field intensities of 210 and 230 mT, both physicochemical properties of MW and the mechanical performance of the MW concrete were optimally enhanced. Under the conditions of a magnetic field intensity of 210 mT and flow velocity of 0.7 m/s, the workability and compressive strength of the concrete prepared with MW improved by 30.4 % and 13.7 %, respectively. These findings highlighted the importance of considering the combined effects of magnetization parameters when optimizing the mechanical properties of MW concrete.

Physicochemical Properties of Water in Contact with Nanobubbles Generated by CO2‐Hydrate Dissociation: An Investigation from Experiment and Molecular‐Dynamics Simulation

AbstractThe study investigates CO2‐nanobubbles (NBs) generated from gas‐hydrate dissociation, exploring their impact on the physicochemical properties of liquid water. Raman spectroscopy evidenced a slight increase in the Raman‐band intensity, suggesting enhanced total hydration‐layer water‐dipole moment and polarity without affecting water molecule structuring. Furthermore, an overall decreasing trend for the zeta potential of NB solution can be observed due to the strong electron affinity on the surface of CO2 bulk NBs, probably caused by a negative charge accumulation. These findings are in good qualitative accord with molecular‐dynamics (MD) simulation results, wherein water can induce a small dipole moment of about 0.16 D for CO2 NBs, thereby increasing the polarity of the system. Due to the interaction between water molecules, the Coulombic or electrostatic forces increase in the presence of NBs compared to pure water, which can reflect the increase in the dipole moment of water molecules in the presence of NBs. The presence of NBs strengthens the local hydrogen‐bond network, leading to higher‐frequency vibrations. Additionally, NBs amplify the intrinsic electric field of the aqueous solution, causing the gas‐water interface to exhibit negatively charged characteristics, dependent on NB size. Molecular simulations agree qualitatively with experiments, emphasizing their utility in studying NB evolution in water.

Electrified Nano-Gaps Under AC Field: A Molecular Dynamics Study

Solid-Liquid Interfaces (SLIs) hold immense significance in various areas such as materials science, chemistry, physics, biology and medicine [1]. Many studies aim to decipher the molecular details of SLIs through analytical, computational or experimental methods [2]-[3], each optimized for different aspects of SLIs. Analytical methods are mainly based on the mean field approximation and work best for dilute solutions. Computational methods are bound by their maximum accessible time and length scales, while the limitation of experimental approach tend to lie in minimum values accessible of these scales. The concomitant deployment of both the approaches is a powerful tool in studying SLIs.In the current study both the computational and experimental tools are employed to study the interface of silica with aqueous saline solutions under electric fields. Molecular Dynamics (MD) simulation are utilized to investigate the relative response of the ions and waters exposed to an external AC field in a nanoscale silica-elecrolyte-gold system. Complementary experimental measurements are conducted with atomic force microscopy (AFM) which measures the dielectric force exerted on the nanoscale AFM probe. The impact of external factors such as salt concentration, AC voltage frequency and the system size is systematically investigated.Simulations reveal both the transient and stable response of water and ions as the main component of the system to the AC field. In the transient response, the water electric dipole increases monotonically with the voltage at the first cycle while it takes longer for ions to react to the field, limited by their diffusion time. When the ionic response becomes large enough to screen the field, the dipole moment of water molecules decreases and lead the phase of the applied field. The lag in the ionic response is owing to the time required for the ionic diffusion, while the lead in the water response is due to ionic lag.To obtain the stable response through MD simulation, Fourier transform was deployed with the results showing that electric dipole of ions and water have a periodic behavior with a frequency similar to the AC field and waters in lead and ions in lag. The dipole-voltage plots for ions and waters depicted an energy transfer between water and ions in each cycle. Decreasing the frequency to 10MHz, no energy exchange was observed concomitant to the removal of water lead. Besides, in the frequency range of 100MHz-200MHz in which the water phase lead reaches its maximum value, there is also a maximum in the energy exchange. Thus, there is a direct relation between the water-ion energy exchange and lead in the water response.The stable response is affected by various factors including the separation distance between the surfaces, the ionic concentration and the AC frequency. The MD observations of a decrease in the water lead and ionic lag with reducing the electrolyte gap could explain AFM measurements where the dielectric force appears to decrease for small gaps, a counter-intuitive result if bulk electrolyte properties are assumed. The simulation results also show that the sum of the electric dipole of water and ions is always in phase with the applied voltage implying that the field is totally screened by the combination of both of them. To provide the same amount of screening in larger separation distance the electric dipole of ions has to increase to counteract its larger lag which is observed in the ionic dipole values. As the ionic dipole despite water molecules are caused by translational entropy, larger ionic dipole translates to larger forces which is observed in the AFM experiments.[1] Taketoshi et al. Japanese Journal of Applied Physics (2021).[2] T. Fukuma and R. Garcia, ACS nano (2018).[3] J.M. Andanson and A. Baiker, Chemical Society Reviews (2010).

Electrolyte effects on the alkaline hydrogen evolution reaction: A mean-field approach

This paper introduces the combination of an advanced double-layer model with electrochemical kinetics to explain electrolyte effects on the alkaline hydrogen evolution reaction. It is known from experimental studies that the alkaline hydrogen evolution current shows a strong dependence on the concentration and identity of cations in the electrolyte, but is independent of pH. To explain these effects, we formulate the faradaic current in terms of the electric potential in the double layer, which is calculated using a mean-field model that takes into account the cation and anion sizes as well as the electric dipole moment of water molecules. We propose that the Volmer step consists of two activated processes: a water reduction sub-step, and a sub-step in which OH− is transferred away from the reaction plane through the double layer. Either of these sub-steps may limit the rate. The proposed models for these sub-steps qualitatively explain experimental observations, including cation effects, pH-independence, and the trend reversal between gold and platinum electrodes. We also assess the quantitative accuracy of the water-reduction-limited current model; we suggest that the predicted functional relationship is valid as long as the hydrogen bonding structure of water near the electrode is sufficiently maintained.

Outstanding Properties of the Hydration Shell around β-d-Glucose: A Computational Study.

Ab initio molecular dynamics (AIMD) simulations have been performed on aqueous solutions of four simple sugars, α-d-glucose, β-d-glucose, α-d-mannose, and α-d-galactose. Hydrogen-bonding (HB) properties, such as the number of donor- and acceptor-type HB-s, and the lengths and strengths of hydrogen bonds between sugar and water molecules, have been determined. Related electronic properties, such as the dipole moments of water molecules and partial charges of the sugar O atoms, have also been calculated. The hydrophilic and hydrophobic shells were characterized by means of spatial distribution functions. β-d-Glucose was found to form the highest number of hydrophilic and the smallest number of hydrophobic connections to neighboring water molecules. The average sugar-water H-bond length was the shortest for β-d-glucose, which suggests that these are the strongest such H-bonds. Furthermore, β-d-glucose appears to stand out in terms of the symmetry properties of both its hydrophilic and hydrophobic hydration shells. In summary, in all aspects considered here, there seems to be a correlation between the distinct characteristics of β-d-glucose reported here and its outstanding solubility in water. Admittedly, our findings represent only some of the important factors that influence the solubility.

Influence of water penetration on glass fiber-epoxy resin interface under electric field: A DFT and molecular dynamics study

Water penetration is a primary cause of composite insulator core rod deterioration. The performance of the glass fiber-epoxy resin (GFEP) interface plays a crucial role in determining the overall performance of the core rod, and the interface is also affected by an electric field. In this study, molecular dynamics (MD) simulation, reactive force field (ReaxFF), and density functional theory (DFT) simulation techniques were employed to analyze the changes in various parameters, including interface binding energy, free volume, Mayer Bond Order (MBO), hydrogen bond number and distribution, chemical groups, radial distribution function (RDF), and others. The influence of the electric field on these parameters was investigated based on the operational conditions. The results showed that the electric field yielded little effect on the dry GFEP model. However, in the presence of water penetration, the system exhibited a “swelling-collapse” phenomenon under the electric field, and the free volume will increase with the increase of the electric field strength. Analysis of hydrogen bond number, water molecule dipole moment, and water molecule RDF indicated that the electric field could induce the polarization of water molecules, causing their migration towards the epoxy resin ester groups and glass fiber, and form hydrogen bond interaction with them respectively. Consequently, the effective hydrogen bond between the glass fiber and epoxy resin decreased. Additionally, DFT simulation showed that the electric field altered the energy of frontier molecular orbitals, promoting the decrease in the MBO of the epoxy resin ester group C-O bond and water molecule O–H bond, thereby increasing the chemical reactivity between the epoxy resin and water molecules, and facilitated the hydrolysis of the glass fiber and epoxy resin. The synergistic effects of these processes ultimately led to interface failure. This research sheds light on the effects of water penetration on the interface between glass fiber and epoxy resin under the influence of an electric field, which is important for improving the overall performance of composite insulators.

Probing the mechanism of salts destroying the cage structure of methane hydrate by molecular dynamics simulation

Much attention has been generated in the exploitation of natural gas hydrate by injecting brine due to its low cost and eco-friendliness. However, it is not clear how inorganic salts destroy the cage structure of methane hydrate. This work focuses on the mechanism of inorganic salts destroying the cage structure of methane hydrate by molecular simulation. And the influence of cation type on methane hydrate decomposition is studied in detail. The results show that inorganic salts can effectively reduce the temperature required for methane hydrate decomposition. And inorganic salts can weaken the interaction between water molecules by reducing the dipole moment of water molecules in methane hydrate, then the cage structure of methane hydrate is destroyed. Methane hydrate both can completely decompose without and with CaCl2 solution at 307 K and 20 MPa, but the decrease rate of the dipole moment autocorrelation function (DACF) of water molecules in the system with CaCl2 solution is 6.10 times than that without CaCl2 solution, and the decomposition rate of methane hydrate increased by 5.8 times because of adding CaCl2 solution. In addition, the increasing charge and radius of cations result in greater methane hydrate decomposition which is caused by the faster destruction speed of cage structure, the faster rate of methane molecules escaping from cage structure and the faster diffusion velocity of cations are demonstrated. This study provides a theoretical basis for the efficient exploitation of methane hydrates by brine injection.

Effects of surface wettability on (001)-WO[formula omitted] and (100)-WSe[formula omitted]: A spin-polarized DFT-MD study

An extensive understanding of WO3 and WSe2 bulk crystalline structures and explicit solvent effects on (001)-WO3 and (100)-WSe2 facets are essential for design of efficient (photo) electrocatalysts. The atomistic level understanding of both WO3 and WSe2 bulk solids and how water solvation processes occur on WO3 and WSe2 facets are nowadays characterized by a noticeable lack of knowledge.Herein, forefront Density Functional Theory-based molecular dynamics have been conducted for assessing the role of an explicit water environment in the characterization of solid surfaces. Water at the interface and H-bonds environment, as well as WO3 and WSe2 surface activity, will be described in terms of surface wettability and interfacial water dynamics, revealing the relevance of treating explicitly liquid water and its dynamics in assessing catalytic features. We provide pieces of evidence of the hydrophobic character shown by (001)-WO3 and (100)-WSe2 facets. A preferential in-plane hydration structure of the first water layer has been detected at both (001)-WO3 and (100)-WSe2 water interface, in which the electric dipole moment of water molecules is re-oriented in a sort of 2-dimensional H-bond network. Bulk property calculations of WO3 and WSe2 are also provided.

Effect of external electric field on the terahertz transmission characteristics of electrolyte solutions* *Project supported by the National Natural Science Foundation of China (Grant No. 61575131).

We fabricated a microfluidic chip with simple structure and good sealing performance, and studied the influence of the electric field on THz absorption intensity of liquid samples treated at different times by using THz time domain spectroscopy system. The tested liquids were deionised water and CuSO4, CuCl2, NaHCO3, Na2CO3 and NaCl solutions. The transmission intensity of the THz wave increases as the standing time of the electrolyte solution in the electric field increases. The applied electric field alters the dipole moment of water molecules in the electrolyte solution, which affects the vibration and rotation of the whole water molecules, breaks the hydrogen bonds in the water, increases the number of single water molecules and leads to the enhancement of the THz transmission spectrum.

Infrared spectroscopy of an endohedral water in fullerene.

An infrared absorption spectroscopy study of the endohedral water molecule in a solid mixture of H2O@C60 and C60 was carried out at liquid helium temperature. From the evolution of the spectra during the ortho-para conversion process, the spectral lines were identified as para-H2O and ortho-H2O transitions. Eight vibrational transitions with rotational side peaks were observed in the mid-infrared: ω1, ω2, ω3, 2ω1, 2ω2, ω1 + ω3, ω2 + ω3, and 2ω2 + ω3. The vibrational frequencies ω2 and 2ω2 are lower by 1.6% and the rest by 2.4%, as compared to those of free H2O. A model consisting of a rovibrational Hamiltonian with the dipole and quadrupole moments of H2O interacting with the crystal field was used to fit the infrared absorption spectra. The electric quadrupole interaction with the crystal field lifts the degeneracy of the rotational levels. The finite amplitudes of the pure v1 and v2 vibrational transitions are consistent with the interaction of the water molecule dipole moment with a lattice-induced electric field. The permanent dipole moment of encapsulated H2O is found to be 0.50 ± 0.05 D as determined from the far-infrared rotational line intensities. The translational mode of the quantized center-of-mass motion of H2O in the molecular cage of C60 was observed at 110 cm-1 (13.6 meV).

Why Interstellar Ice Dust Grains Should Be Elongated

Abstract Models of interstellar dust alignment assume that dust grains are elongated, but none of these models explain why dust grains should be elongated. On the other hand, models of interstellar dust grain growth assume that dust grains are spherical and not elongated. We show that when dusty plasma effects and the dipole moment of water molecules are together taken into account, ice grains in interstellar space should be prolate ellipsoids and not spheres. Dusty plasma analysis shows that an ice grain is charged to a negative potential that has magnitude nearly equal to that of the electron temperature. Several different mechanisms causing deviation from sphericity are identified; these mechanisms involve the interaction of the dipole moment of water molecules with electric fields associated with ice grain charging. These mechanisms include the focusing of water molecule trajectories, the migration of water molecules in a quasi-liquid layer on the grain surface toward regions where the electric field is strongest, the enhancement of this migration by the bombardment of energetic protons that gain energy upon falling into the ice grain negative potential, and mutual repulsion by electric charges having the same sign. The aspect ratio is established shortly after the ice grain is formed, and then is maintained as the grain grows.

Solvation in ionic liquid-water mixtures: A computational study

Solvation in mixtures of 1-ethyl-3-methylimidazolium acetate ionic liquid with water in a molar concentration of 5% is studied by means of atomistic molecular dynamics (MD) simulations. We employed a spherical coarse-grained parameterization to describe a model solute and we performed MD simulations with positively charged, negatively charged and neutral model spheres and compare the results with those previously reported in pure ionic liquids. Our study reveals that water does not significantly perturb the structure of the electric double layer neither the orientation of ions in the neighborhood of the solute particle. Although water does not seem to play any significant role in the solvation of neutral solutes, there is an excess of water in the first and second ionic solvation shell of both charged solutes, respectively. We also studied the correlation between the electric field around the negatively charged model solute and the orientation of the dipole moment of water molecules, finding that, although the dynamic properties of water molecules are almost unaltered in the presence of the solutes, and the ionic cage around the central solutes is only slightly affected upon water addition, the mobility of the spheres is drastically enhanced.

Selectivity of Carbon Nanotubes under An Electric Field on Transferring Water – Alcohol Mixtures

Carbon nanotubes (CNTs) have shown a great promise for nanofluidic-based applications such as for separation membranes. Water confined in nanotubes has different properties compared with those in bulk. Therefore, to develop a membrane with CNTs, it is very important to clarify the behavior of water in CNTs. In this study, we show effects of an electric field on water in a CNT by molecular dynamics simulation. An electric field aligns the dipole moment of water molecules and induces formation of an ordered structure in a CNT. As a result, the electrostatic interaction between water molecules within the structure becomes stronger. Strengthening of the electrostatics interaction facilitates water molecules preferring to fill a CNT over alcohol molecules. This indicates a strong separation effect for water-alcohol solutions.

Calculation of the Space Charge Layer Thickness with Account for the Dipole Moment of Water Molecules in KCl and NaCl Solutions

The problem of the electric double layer in electrolytes is considered. The Poisson equation is integrated with account for the screening of electrodes by salt ions and water molecules. The space charge layer has been calculated. The volt–ampere characteristics in NaCl and KCl solutions are presented. A method for determining the temperature of ions from the volt–ampere characteristic of the electrolyte solution is proposed.

Molecular Dynamics Simulation: Influence of External Electric Field on Bubble Interface in Air Flotation Process

Molecular dynamics(MD) simulation was performed to investigate the influence of external electric field on the vapour-liquid interface of the bubble during the process of toluene separation by air flotation. The physico-chemical properties of vapour-liquid interface, surface tension, probability of a hydrogen bonding near the vapour-liquid interface and the viscosity of liquid phase caused by external electric field were analyzed. The results show that the angle between the water molecule dipole moment and the normal z axis in the vapour phase changes smaller when the external electric field is applied. The surface tension and the probability of hydrogen bonding near the vapour-liquid interface increase with the increase of electric field strength. And the viscosity also increases under an external electric field. The results confirm that the external electric field has a positive effect on the performance of bubbles in air flotation, which may provide useful guidance for the combination of electric field and air flotation technology.

Adsorption of water on fluorinated graphene

In this paper, we investigate the adsorption of water monomer on fluorinated graphene using state-of-the-art first-principles methods within the framework of density functional theory (DFT). Four different types of methods are employed to describe the van der Waals (vdW) interactions between water molecule and the carbon surface: The traditional DFT calculations within the generalized gradient approximation (GGA), and three additional types of calculations using respectively the semi-empirical DFT-D2 method, the original van der Waals density functional (vdW-DF) method, and one of its variants. Two situations and totally four adsorption configurations are considered. Compared with the adsorption on pristine graphene, the adsorption energies of water on fluorinated graphene are significantly increased, and the orientations of water diploe moment are notably changed. The most stable configuration is found to stay right above the top site of the C atom which is bonded with F, and the dipole moment of water molecule aligns spontaneously along the surface normal.

Further Progress in the Electrostatic Nucleation of Water Vapor

The planet's atmosphere holds a vast amount of water. Existing state-of-the-art “atmospheric water generation” systems mostly work by cooling the entire air flow below the dew point, which require significant amounts of energy per liter of water. As a result, the cost of this water is similar to that of imported bottled water in small single-use plastic containers. Therefore, there is an urgent need for any technology that generates usable water in an energy-efficient manner. It is known that the native dipole moment of water molecule results in the nucleation of liquid phase on carriers of electrical charge due to the suppressed evaporation. Nevertheless, the practical implementation of electrostatic water nucleation (EWN) is still in the stage of laboratory demonstrations. This work summarizes the theoretical background of the phenomenon and past experimental data, presents further experimental results and new data from practical implementation of EWN, and analyzes options for the further development.

Structural and dipolar fluctuations in liquid water: A Car–Parrinello molecular dynamics study

A Car–Parrinello molecular dynamics simulation was performed to investigate the local tetrahedral order, molecular dipole fluctuations and their interrelation with hydrogen bonding in liquid water. Water molecules were classified in three types, exhibiting low, intermediate and high tetrahedral order. Transitions from low to high tetrahedrally ordered structures take place only through transitions to the intermediate state. The molecular dipole moments depend strongly on the tetrahedral order and hydrogen bonding. The average dipole moment of water molecules with a strong tetrahedral order around them comes in excellent agreement with previous estimations of the dipole moment of ice Ih molecules.

Dipole Moment and Binding Energy of Water in Proteins from Crystallographic Analysis

The energetics of water molecules in proteins is studied using the water placement software Dowser. We compared the water position predictions for 14 high-resolution crystal structures of oligopeptide-binding protein (OppA) containing a large number of resolved internal water molecules. From the analysis of the outputs of Dowser with variable parameters and comparison with experimental X-ray data, we derived an estimate of the average dipole moment of water molecules located in the internal cavities of the protein and their binding energies. The water parameters thus obtained from the experimental data and analyzed within the framework of charge-scaling theory; the parameters are shown to be in good agreement with the predictions that the theory makes for the dipole moment in a protein environment. The water dipole in the protein environment is found to be much different from that in the bulk and in such models as SPC or TIPnP.

The entropic forces and dynamic integrity of single file water in hydrophobic nanotube confinements.

Water in nanotube exhibits remarkably different properties from the bulk phase, which can be exploited in various nanoconfinement based technologies. The properties of water within nanotube can be further tuned by varying the nanotube electrostatics and functionalization of nanotube ends. Here, therefore, we investigate the effect of quantum partial charges and carbon nanotube (CNT) termination in terms of associated entropic forces. An attempt has been made to correlate the entropic forces with various dynamical and structural properties. The simulated structural features are consistent with general theoretical aspects, in which the interfacial water molecules at H terminated CNT are found to be distributed in a different way as compared to other CNTs. The rotational entropy components for different cases of CNTs are well corroborated by the decay time of hydrogen bond (HB) correlation functions. A part of this event has been explained in terms of orientation of water molecules in the chain, i.e., the change in direction of dipole moment of water molecules in the chain and it has been revealed that the HBs of CNT confined water molecules show long preserving correlation if their rotations inside CNT are restricted. Furthermore, the translational entropy components are rationally integrated with the differing degree of translational constraints, added by the CNTs. To the best of our information, perhaps this is the first study where the thermodynamic effects introduced by H-termination and induced dipole of CNT have been investigated. Additionally, we present a bridge relation between "translational diffusivity and configurational entropy" for water transport from bulk phase to inside CNTs.